[XCB] Fix drag-and-drop segfault

QXcbDrag inherits QBasicDrag which takes care of calling
updateAction() when needed, we don't need to call it explicitly.

Task-number: QTBUG-33057

Change-Id: I754408f74f56de36ace8ffa40a61bd7c64619899
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

src/plugins/platforms/xcb/qxcbdrag.cpp

@@ -872,7 +872,6 @@ void QXcbDrag::handleLeave(QWindow *w, const xcb_client_message_event_t *event)
     }
 
     QWindowSystemInterface::handleDrag(w,0,QPoint(),Qt::IgnoreAction);
-    updateAction(Qt::IgnoreAction);
 
     xdnd_dragsource = 0;
     xdnd_types.clear();